Manufacture of agglomerated bodies from blast-furnace dust.



narrate i a at. thumb-Jami '.L U .a set.

NILHELM SCHUMACHER, GIG OSNABPXUCK, GERMANY.

MANUFACTURE OF AGGLOMERATED BODIES FROM BLAST-FURNACE DUST.

933.2% Specification of La.

No Drawing. Application filed June 10, 1908.

could he made from blast furnace dust only with the addition of a greater amount of binding material than required by other substances, for instance by ores of the same fineness. The very powdery nature of the blast furnacedust proved to be a feature adding to the diilicult-y of the problem. it is true that as a rule fineness of the stuff is believed to increase the facility of producing agglomeration. and certainly blast furnace dust is a material of greatfineness, being even tiner than most grades of Portland cement; very often much as 90% of the blast furnace dust will pass through a sieve of 900 meshes per square inch. and 01 it through a sieve of 5000 meshcs to the square inch. Notwithstanding this great fineness, ordinary blast furnace dust otters difliculties to its agglomeration. The reason of this lmhavior I find in the approximately spher ical form. which the grains of blast furnace dust exhibit when viewed under a microscope, this form being due to the rubbing and perhaps to the sinteringof all fine. points and edges as a result of the"strong pressure of the air blast in the blast t'urnace. Particles of this approximately spherical form, although very fine. will not properly unite into a coherent body. even under high pressure such as used in briqueb ing. For instance, a briquet made from blast furnace dust under a pressure of 200 kg. per square cm. with a 15% addition of binding material, is still capabie of absorbing as much as 20% of water, thus proving the existenceof a considerable aggregate of voids in the briquet.

In order to overcome the ditticulty above mentioned and to enable the blast furnac. dust, to be more readily formed into coher ent bodies, I destroy the apprmtimately spherical shape of the particles by grinding Patent Patented Sept. 7. "l

"lerial N0. 437.6%7.

the wast furnace dust, which maybe done in .ube mill or a pulverlzmg mill such as are sed 1n the cement industry. This operrtion produces irregular splinter) and more or less sharp-edged bodies or needles from the approximately spherical grains of l)l2l. t furnace dust. The material is then in a condition of much higher compressibility. so that when formed into briipiets sit and solidity become much greater than when the. blast furnace dust is used in its original condition in which it is composed of a mroximately spherical bodies.

The grinding also presents another ad vantage. particularly when applied to trcsh its denblast furnace dust which has not become hydrated. l have t'ound that the grnulng liberates. as it were. some binding substances contained in the blast furnace dust. which binding substances enablethe material to be briqnetcd or agglomerated in some cases without the use of any additional bind ng material. the mass hardening under ertain conditions very much like cement. This binding action otl tinely ground blast turnace dust is so great that it may be utilized not only for agglomcrating thc blast t'urnaee dust itself. but t'or agglomerating other substances such as fine ores. the blast furnace dust in this case forming the binder. I may therefore produce agglomerated bodies from blast furnace dust ground as explained above. by simply moistening the material with water. t'orming it. into lumps or blocks by pressure or otherwi. and then exposing it to the action of the air to cause. it to harden. This process may be carried out with the blast' 'l llllltlfl dust alone. or with the addition oi other fine materials. such as line ores or blast turnace slag. The hardening ot the mass may be obtained by exposure to air as stated above, or by heating in the open air. or by treating the lumps or blocks with steam under pressure in a closed receptacle.

I may also, in some cases. add bindin; materials it the binding action of the blast furnace dust should not. be strong enough. Any ot the usual binding materials may be employed. l have found that certain salts and acids are particularly available tor use as binding materials in my process. (blorids. (except. those of the alltalies) sulfates, sulfids. partitallarly those of the alkaline earth metals and those of metals ot the iron group are best adapted for this purpose. The particular salt, or mixture of salts best suited for each individual blast furnace dust has to be ascertained by experiment. The

corresponding acids such as sulfuric acid,

sulfurous acid and hydrochloric ac d, etc. These acids then form soluble salts with certain ingredients of blast furnace dust, such as the iron contained therein. The action of these salts is chiefly a catalytic one, that is, they do not themselves form chemical compounds possessing any material binding power. Of course, salts of this character may be'used in connection with other suitable binding materials, but care should be taken not to employ a binding material hav-' ing strongly alkaline properties, as this would interfere with the proper action of said salts. For this reason ordinary Portland cement should not be used as a binding material in conjunction with the catalytic salts above mentioned, since it would evolve hydrated lime, which will have a restrainingaction on the catalytic action of the salts. if, therefore, any binding materials are added. which contain lime, they should be so selected that their binding action by the evolution of hydrate of lime will not. take place until after the blast furnace dust has been hardened entirely, or at least for the greater part.

I claim as my invention:

1. The herein described process of ag glomerating blast furnace dust, which coir sists in grinding such dust so as to transform its approximately spherical grains into fragments of irregular shape and then form'- ing the mass into coherent bodies.

2. The herein described process of ag glomerating blast furnace dust, which con sists in grinding such dust so as to transform its approximately spherical grains into fragments of irregular shape, moistening the mass and forming it into coherent bodies.

3. The herein described process of agglomerating blast; furnace dust, which consists in grinding such dust so as to transform its approximately spherical grains into fragment-s of irregular shape, adding to the mass substances having a catalytic influence upon the hardening process and forming the mixture into coherent bodies.

4. The herein, described process of ag glomerating blast furnace dust, which consists in grinding such dust so as to transform its approximately spherical grains into fragments of irregular shape and adding a suitable binding material and forming the mixture into coherent bodies.

The herein described process of ,ag-

glomerating blast furnace dust, which consists in grinding such dust so as to transform its approximately spherical grains into fragments of irregular shape, addin to the mass other binding material together with substances having a catalytic action on the hardening process, and forming the mixture into coherent bodies.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

\VILHELM SCHUMACHER.

Witnesses HENRY llasrnn,

' \VoLnnMAR HAUr'r. 

